Antihydrogen Formation via Antiproton Scattering with Excited Positronium

Utilizing the two-center convergent close-coupling method, we find a several order of magnitude enhancement in the formation of antihydrogen via antiproton scattering with positronium in an excited state over the ground state. The effect is greatest at the lowest energies considered, which encompass those achievable in experiment. This suggests a practical approach to creating neutral antimatter for testing its interaction with gravity and for spectroscopic measurements.

Figure 1

Total cross sections for positronium atoms, in the specified initial state $nl$, scattering on (anti)protons to form (anti)hydrogen calculated by using the CCC method; see the text. For $\mathrm{Ps}(1s)$, the variational calculations [13, 38, 39] are for (anti)hydrogen formation in the $1s$ state only (CCC-calculated unconnected points presented for comparison), while the UBA calculations of Mitroy [17] and Mitroy and Stelbovics [16], and the CCC calculations generally, are for (anti)hydrogen formation in all open states. The three experimental points are due to Merrison et al. [27].